Over the years, there has been a variety of approaches to treating and disposing of livestock manure as well as mediating disagreeable odor generated from livestock manure. The increased scrutiny is due in part to or as a result of a well-known recent trend toward higher concentrations of livestock. As a result, land, water and other natural resources must be better utilized to accommodate and sustain higher concentrations of livestock.
In 2003, the Environmental Protection Agency (EPA) estimated that there were 1.3 million farms in the U.S. maintaining livestock. About 238,000 of these farms were considered to be Animal Feeding Operations (AFOs). AFOs produce more than 500 million tons of animal manure that, when improperly managed, poses substantial risks to the environment and public health. More recently, however, problems associated with livestock manure have become more challenging due to increased environmental and other regulatory scrutiny.
Also in 2003, the EPA issued final rules revising and clarifying regulatory requirements for Concentrated Animal Feeding Operations (CAFOs) pursuant to the Clean Water Act. (33 USC § 1251(a))(40 CFR Parts 9, 122, 123 and 412). These rules seek to ensure that CAFO's act to manage manure more effectively and protect the nation's water quality. At present, the EPA estimates that there are 15,500 CAFOs managing 300 million tons of manure produced annually. CAFOs often have insufficient land to effectively use the manure as fertilizer. That trend coincides with increased reports of large-scale discharges from CAFOs as well as continued nutrient runoff impairing U.S. water bodies. Interestingly, the EPA also estimates that confined farm animals generate 3 times more raw waste than is generated by humans in the U.S.
The EPA's new regulatory program covering the large CAFO operations (which present the greatest potential risk to water quality) is consistent with the Unified National Strategy for Animal Feeding Operations jointly developed by the EPA and the U.S. Department of Agriculture (USDA). The strategy defines a national objective for all AFOs to develop a comprehensive nutrient management plan to minimize impact on water quality and public health.
Despite improvements in water quality since passage of the Clean Water Act, nearly 40% of the Nation's assessed waters remain impaired. The EPA has determined that manure from CAFO's is a significant contributor to the remaining water quality problems. Put simply, improperly managed manure has caused serious chronic and acute water quality problems throughout the U.S.
The new rules strengthen the existing regulatory program relating to CAFO's by establishing a mandatory duty to apply for a permit pursuant to the National Pollutant Discharge Elimination System (NPDES)(42 CFR § 122) and the Effluent Limitations Guidelines and Standards (ELGs) for CAFOs (42 CFR § 412). To obtain the NPDES permit, the CAFO must develop and implement a nutrient management plan in compliance with effluent guidelines that set forth performance expectations for existing and new sources. The performance expectations address appropriate manure storage and proper land application practices for CAFOs. The management plan also identifies site-specific actions to be taken by the CAFO to ensure proper and effective manure and wastewater management.
In the past, livestock manure has been treated by anaerobically digesting raw livestock manure. In this process, a mixed culture of bacteria mediates the degradation of the putrescible fraction of organic matter ultimately to methane, carbon dioxide and mineralized nutrients. However, volatile intermediate compounds are also produced that have a foul odor. Another known method uses a fixed film digester design for anaerobic digestion of flushed livestock manure, whereby a biofilm allows effective treatment of wastewater at ambient and elevated temperatures as well as at reasonable hydraulic retention times.
Other systems combust animal waste to avoid releasing objectionable odor and produce dry ash that can be used as fertilizer. Another known system extracts heat energy from manure and other wet waste by combusting waste that had been dried, whereby the waste material is combusted to ash. Yet another known system makes fuel from livestock, industrial and agricultural waste and other biomass wastes, whereby the waste materials are blended and formed into fuel pellets without the need for mechanical or drying processes.
Others have designed processes for sterilizing, dewatering and micronizing organic and biomass waste streams to produce liquid or granular fertilizer, and similar systems for drying, deodorizing, sterilizing and pulverizing animal waste and manure to produce fertilizer. Still other systems compress (i.e., dewatering) and/or bio-digest various biomasses, manure and various sludge or slurries, whereby opposing rollers and a friction-inducing differential are used to produce organic fertilizer or soil conditioner.
Another known system makes organic fertilizer pellets from raw manure using cyclones that generate high-velocity air streams to pulverize and dry the raw manure. Another known system recycles organic household and restaurant waste to produce a pro-ferment, whereby the pro-ferment is mixed with animal waste to compost fermentation. Another known system manufactures artificial soil, soil conditioner, peat substitute or hygienic bedding material for livestock from animal excrement whereby the manure is deodorized, sterilized and rendered porous by subjecting the manure to an alternating current in a reactor.
It is well known in the art that livestock manure is problematic. For example, odor generated by large concentrations of manure is offensive and noxious. Disposal of livestock manure is also problematic for environmental safety reasons such as: erosion control, manure storage, runoff control, nutrient management, water/wetland protection, land runoff pollution, phosphorous and nitrogen emission reduction, and EPA regulations concerning CAFOs. Thus, it is highly advantageous to treat livestock manure in such a way as to avoid or minimize emitting odor and to avoid significant disposal. Prior attempts have been made to dry and combust manure. However, there remains a need to convert animal manure into useful end-products in new and more effective ways.